1. Field of the Invention
The present invention relates, in general, to magnetic tape head assemblies for use in conjunction with magnetic recording media such as tape, and more particularly to thinfilm tape heads including one or more thinfilm thermosensors on active or inactive islands for sensing operating temperatures at the interface between the tape head islands, where read and write elements are located, and the moving tape (e.g., the media interface).
2. Relevant Background
Data storage on tape accounts for a large portion of the sales of data storage products. In part, this is a result of the continuous improvement of recording media (i.e., tape) and read/write heads to try to increase magnetic tape drive performance and capacity. The data-bearing side of the media or tape is typically composed of microscopic magnetic particles dispersed in a polymeric binder and coated onto a flexible substrate. Recent improvements in tape have been achieved through the use of advanced metal power technologies and through the use of metal evaporation.
Recently, advanced thinfilm processing technology has been used to fabricate densely packed magnetoresistive tape heads (sometimes called magnetoresistive cluster (MRC) heads) to obtain higher data transfer rates and greater data density than traditional ferrite and metal heads which generally have comparatively bigger size. Tape heads typically contain one or more raised strips or islands that have surfaces over which the magnetic recording media, e.g., tape, passes. Embedded in active islands are transducers which may be recording transducers (i.e., recording or writing elements) for writing information (i.e., bits of data) onto the media or reproducing transducers (i.e., reproducing or reading elements) for reading information from the media. An embedded recording transducer produces a magnetic field in the vicinity of a small gap in the core of the recording transducer that causes information to be stored on the magnetic media as it streams across the support surface. In contrast, a reproducing transducer detects a magnetic field near the surface of the magnetic media in the vicinity of a small gap as the media streams over the support surface. Lead and follow inactive islands are often optionally provided for initially contacting the tape to create a desired wrap angle or control the contact at the active islands. The inactive islands also provide sharp edges to scrape away any unwanted magnetic or non-magnetic particles prior to the particles contacting the read/write elements. The contact and partial-contact surfaces on both active and inactive islands form a contour tape bearing surface (TBS).
There is typically some microscopic separation between the gap of the transducer core and the recording media. During operation, this separation must be tightly monitored and controlled to minimize “spacing loss.” The separation reduces the magnetic field coupling between the recording transducer and the media during writing and between the media and the reproducing transducer during reading. While a higher, more easily obtainable amount of head-to-media separation may be acceptable at low recording densities, the growing demand for higher recording densities has led to the need for tighter control over the head-to-media separation that can be tolerated to obtain useful levels of magnetic coupling. To control spacing loss, a tension is applied to the tape as the tape passes at a wrap angle around a support surface or head island. Due to this tension, the tape exerts a pressure against the head island and the ongoing friction causes heat to be generated and the temperature of the island and tape to increase. In some tape head assembly designs, the pressure is intentionally increased to control spacing loss which, in turn, increases the contact zone and friction at the media interface.
While thinfilm heads provide enhanced transfer rates and other operating improvements, the temperature of the interface between the head and media or simply the temperature of the head has proven difficult to monitor during operations. The head and/or interface operating temperature needs to be monitored. If the temperature becomes too high (such as about 50° C. but varying with head and tape materials and fabricating techniques), a loss of thermal stability or thermal degradation of the head and media properties may occur and result in deposition of materials from the media on the head surface and/or degradation of mechanical and magnetic properties of the media. Even when actual degradation does not occur, high temperature operations may result in reduced tape and head durability and a shorter operating life.
During operation, the magnetic media flies rapidly over the tape head which causes contact and partial contact between the head islands and the tape resulting in frictional heat. The amount of frictional heat depends on a number of factors including the wrap angle distribution, the composition and roughness of the media and the islands, the tape tension, and the tape speed. While the tape is moving, air is also being dragged between the tape and head surfaces cooling the tape and head. The rate of air flow also depends upon a number of factors including speed of a cooling fan in the tape drive, tape speed, head contour, and shape and configuration of the tape head vicinity. In addition, electrical currents are passed through the head elements which cause the elements to be resistively and inductively heated and, the amount of operating current is often increased in attempts to obtain higher output to facilitate higher storage densities and better error rates. Further, cooling fans used within tape drive enclosures may not be able to keep operating temperatures at desired levels and the “cooling” air flowing in the interface may be above room temperature. Due to the number and complexity of the heating and cooling parameters, modeling, such as mathematical heat transfer and finite element simulation, have not proven particularly useful in predicting operating temperature at the head-media interface.
Prior attempts to physically monitor operating temperatures have been ineffective at measuring the temperature at the head-media interface. Conventional thermosensors have been used but have not provided an accurate onsite measurement of the interface temperature. Conventional thermosensors are relatively large and cumbersome relative to the size of the thinfilm magnetoresistive head, which makes it difficult to position a conventional thermosensor at a location that provides useful head-media interface temperature measurements. With the tape flying over the TBS, the tape blocks access to the interface. Lack of access to the actual interface area also causes problems when thermal imaging is used to try to monitor the head or interface temperatures. The thermal image can be used to obtain temperatures on the non-data bearing or back side of the tape but not of the data bearing side and not of the head-media interface temperature.
Hence, there remains a need for an improved method and/or system for monitoring the temperature at the interface between a tape head and a magnetic media. Such a thermal stability or interface temperature monitoring method and system preferably would be configured to provide real-time feedback or sensing of onsite temperatures on the islands of thinfilm magnetoresistive heads during the operation of a tape drive. Additionally, such a method and system would be compatible with manufacturing processes used for producing the head and tape drive utilizing the head.